The present invention relates to improvements in multi-cell devices for electrolysis of water by means of d.c. current. The present invention relates particularly but not exclusively to improvements in the type of device as shown in German printed patent application P 2159246 wherein the lower portion of a common container holds such plural cells which are open at their respective top and are electrically connected in series, whereby common anode-cathode electrode sheets with proper insulation divide the electrolytic liquid into the several cells.